Home
Class 12
MATHS
x ^(2) +y ^(2) =a ^(2) is the standard e...

`x ^(2) +y ^(2) =a ^(2)` is the standard equation of a circle centred at `(0,0)` and radius is a.
Paramatric Equation to Standard Circle:
Parametric Equation for the circle `x^(2) +y ^(2) =a ^(2) ` is `x =a cos theta, y =a sin theta.`
Director Circle:
Director circle is the locus of point of intersection of two perpendicular tangents.
Two points `A (-30^(@)) and B (150^(@))` lies on circle `x ^(2) +y ^(2) =9.` The point `(theta)` which moves on a circle such that area of `Delta PAB` is maximum, is/are

A

`60^(@)+2kpi, k in l`

B

`120^(@)+2kpi, k in l`

C

`75^(@)+2kpi , k in l`

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the point \( P \) on the circle \( x^2 + y^2 = 9 \) such that the area of triangle \( PAB \) is maximized, where points \( A \) and \( B \) are given as \( A(-3\sqrt{3}, -3) \) and \( B(3\sqrt{3}, 3) \). ### Step-by-Step Solution: 1. **Identify the Circle and Points**: The equation of the circle is \( x^2 + y^2 = 9 \), which has a center at \( (0, 0) \) and a radius \( r = 3 \). The points \( A \) and \( B \) are located on this circle. 2. **Parametric Equations**: The parametric equations for the circle can be expressed as: \[ x = 3 \cos \theta, \quad y = 3 \sin \theta \] where \( \theta \) is the angle parameter. 3. **Area of Triangle \( PAB \)**: The area \( A \) of triangle \( PAB \) can be calculated using the formula: \[ \text{Area} = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right| \] Substituting \( P(3 \cos \theta, 3 \sin \theta) \), \( A(-3\sqrt{3}, -3) \), and \( B(3\sqrt{3}, 3) \): \[ \text{Area} = \frac{1}{2} \left| 3 \cos \theta \left(-3 - 3\right) + (-3\sqrt{3})(3 - 3 \sin \theta) + (3\sqrt{3})(3 \sin \theta + 3) \right| \] 4. **Simplifying the Area Expression**: Simplifying the expression: \[ = \frac{1}{2} \left| 3 \cos \theta (-6) + (-3\sqrt{3})(3 - 3 \sin \theta) + 3\sqrt{3}(3 \sin \theta + 3) \right| \] \[ = \frac{1}{2} \left| -18 \cos \theta + 9\sqrt{3} \sin \theta + 9\sqrt{3} \right| \] 5. **Finding Maximum Area**: To maximize the area, we can differentiate the area expression with respect to \( \theta \) and set the derivative to zero. However, a more straightforward approach is to recognize that the area is maximized when the height from point \( P \) to line \( AB \) is maximized. 6. **Using Geometry**: The maximum area occurs when \( P \) is perpendicular to the line segment \( AB \). The slope of line \( AB \) can be found, and the angle \( \theta \) can be determined such that \( P \) is directly above or below the midpoint of \( AB \). 7. **Calculating the Midpoint**: The midpoint \( M \) of \( AB \) is: \[ M = \left( \frac{-3\sqrt{3} + 3\sqrt{3}}{2}, \frac{-3 + 3}{2} \right) = (0, 0) \] Since \( P \) must lie on the circle, we can find the angles corresponding to the maximum area. 8. **Finding Angles**: The angles that maximize the area can be determined using the tangent function: \[ \tan \theta = \frac{3}{3\sqrt{3}} = \frac{1}{\sqrt{3}} \implies \theta = 60^\circ \text{ or } 240^\circ \] ### Final Answer: The angles \( \theta \) that maximize the area of triangle \( PAB \) are: \[ \theta = 60^\circ \text{ and } 240^\circ \]
Promotional Banner

Topper's Solved these Questions

  • MATHEMATICS

    FIITJEE|Exercise NUMERICAL BASED QUESTIONS|23 Videos
  • MATHEMATICS

    FIITJEE|Exercise NUMERICAL DECIMAL BASED QUESTIONS|15 Videos
  • MATHEMATICS

    FIITJEE|Exercise MCQ (MULTIPLE CORRECT)|30 Videos
  • MATHEMATICAL REASONING

    FIITJEE|Exercise ASSIGNMENT PROBLEMS (OBJECTIVE) LEVEL-2|18 Videos
  • MATHEMATICS TIPS

    FIITJEE|Exercise NUMERICAL DECIMAL BASED QUESTIONS|21 Videos

Similar Questions

Explore conceptually related problems

x ^(2) +y ^(2) =a ^(2) is the standard equation of a circle centred at (0,0) and radius is a. Paramatric Equation to Standard Circle: Parametric Equation for the circle x^(2) +y ^(2) =a ^(2) is x =a cos theta, y =a sin theta. Director Circle: Director circle is the locus of point of intersection of two perpendicular tangents. A ray of light which comes from (-3,1) travels along a line L and after reflection from the circle x ^(2) +y ^(2) =a ^(2), reficated ray moves along the same line L, then the equation of line L is

The parametric equations of the circle x^(2) + y^(2) + mx + my = 0 are

Locus of point of intersection of perpendicular tangents to the circle x^(2)+y^(2)-4x-6y-1=0 is

Statement-I The equation of the directrix circle to the hyperbola 5x^(2)-4y^(2)=20 is x^(2)+y^(2)=1 . Statement-II Directrix circle is the locus of the point of intersection of perpendicular tangents.

The equation of director circle to the circle x^(2) + y^(2) = 8 is

Equation of Normal at ' theta ' to the circle x^(2)+y^(2)=r^(2) is

IF the locus of the point of intersection of two perpendicular tangents to a hyperbola (x^(2))/(25) - (y^(2))/(16) =1 is a circle with centre (0, 0), then the radius of a circle is

Radius of the circle x^(2)+y^(2)+2x cos theta+2y sin theta-8=0, is

FIITJEE-MATHEMATICS -PARAGRAPH BASED (MULTIPLE CHOICE)
  1. A circle C whose radius is 1 unit, thuches the x-axis at point A. The ...

    Text Solution

    |

  2. Pedal Triangle of a Triangle: Let Delta ABC be any triangle and let D,...

    Text Solution

    |

  3. Consider a three dimensional Cartesian system with origin at O and thr...

    Text Solution

    |

  4. Consider a three dimensional Cartesian system with origin at O and thr...

    Text Solution

    |

  5. Consider a three dimensional Cartesian system with origin at O and thr...

    Text Solution

    |

  6. For each positve real number k, let C (k) denotes the circle with cent...

    Text Solution

    |

  7. For each positve real number k, let C (k) denotes the circle with cent...

    Text Solution

    |

  8. For each positve real number k, let C (k) denotes the circle with cent...

    Text Solution

    |

  9. Consider a fixed parabola C (1) -=x ^(2) + y =0. A set of varying para...

    Text Solution

    |

  10. Consider a fixed parabola C (1) -=x ^(2) + y =0. A set of varying para...

    Text Solution

    |

  11. Any second degree equation ax ^(2) + by ^(2) + 2 hxy + 2gx + 2fy + c =...

    Text Solution

    |

  12. If the equation 12x^(2)+7xy-py^(2)-18x+qy+6=0 represents a pair of pe...

    Text Solution

    |

  13. Suppose we drfine the distance between two points P (x(1), y (1)) and ...

    Text Solution

    |

  14. Suppose we drfine the distance between two points P (x(1), y (1)) and ...

    Text Solution

    |

  15. x ^(2) +y ^(2) =a ^(2) is the standard equation of a circle centred at...

    Text Solution

    |

  16. x ^(2) +y ^(2) =a ^(2) is the standard equation of a circle centred at...

    Text Solution

    |

  17. Solving problems in co-ordinate geometry with given set of conditions ...

    Text Solution

    |

  18. Solving problems in co-ordinate geometry with given set of conditions ...

    Text Solution

    |

  19. An equatin of the family of circles passing through a given pair of po...

    Text Solution

    |

  20. An equatin of the family of circles passing through a given pair of po...

    Text Solution

    |